RMax question for lofting GBU-38 vs 31

[pchRage]

Any idea why on the deck, > 1.0M that the GBU-38 top of the staple RMax is ~4.2nm while the 31 (and 31v3) are around 6nm?

Maybe the guidance kit/fins are larger on the biggie and can semi-glider further?   Feels backwards given the 500 vs 2000lb sizes...

And when your at, say 28k AGL > 1.0M, you can typically hit RMax around 17nm for the -38 vs around 13nm for the -31....

 

[Tholozor]

More mass, more momentum.

[pchRage]

Thanks for the reply! 

And at altitude its flipped the other way (RMax 38 > 31) because of the time gravity can affect the extra weight or ?

[Tholozor]

The effect of gravity affects objects more equally the less air is in the space the objects occupy. It's like vacuum chamber tests with bowling balls and feathers, they fall at the same rate regardless of their mass/weight.

At higher altitudes where the air is thinner, gravity will affect objects more equally since there isn't as much air resistance/drag to slow them down. However once the drag does start to become more of a factor, the 31's body induces more drag as it falls into thicker air, versus the 38 which is much smaller.

The JDAM's guidance kit can also play a factor, as the weapon's trajectory is modified to account for terminal impact settings so that the weapon can arrive at the target at a specified angle/azimuth/rate of descent.

Edited August 25, 2023 by Tholozor